To complete a well for the production of effluents and notably of oil fluids, a casing pipe is generally lowered therein and held in position by injecting cement into the annular space between the casing and the well. Containment of the well is then achieved by covering it with a wellhead through which a tubing is lowered down to the underground zone or reservoir.
Patents FR-2,593,292 and FR-2,642,849 and patent application Ser. No. 91/11,536 filed by the applicant mention well-known methods and devices for installing permanently, behind a casing pipe, seismic or acoustic receivers, possibly associated with electronic signal processing assemblies, and connected to a surface installation by means of one or several multiline transmission cables. These cables run up to the surface on the outside of the casing and are also embedded in the coupling cement. This kind of linkage with cables has drawbacks. To connect the various lines of these cables to a control and recording station, they have to be run through the wellhead. This requires installation of a wellhead provided with special connectors with sealed terminals or possibly modification of an existing wellhead. Furthermore, difficulties may arise upon cementing of the casing. In fact, the casing may sometimes have to be moved or rotated around its axis so as to better distribute the cement injected and to improve the coupling. It may sometimes happen that the cables are damaged during these operations and that communication with some of the receivers installed in the well is defective. Besides, the presence of cables in the annulus may lead to escape ways for the gaseous effluents contained in the formation crossed by the well.
Published French Patent Applications FR-2,656,034, 2,673,672 and 2,674,029 refer to devices and methods for implementing stationary receivers installed outside a tubing, in the annular space between the tubing and the well or the casing thereof. Like those installed outside a casing, they are connected to a surface control and recording station by means of multiline cables which also have to cross the wellhead through sealed terminals, with the same drawbacks.
There is a well-known process for carrying out measurements in wells by means of accessible measuring instruments. When the production of a reservoir is to be monitored in situ and some significant parameters are to be measured: pressure, temperatures, etc, it is well-known to use tubular strings some sections of which are fitted with bulges inside which side pockets are provided for instruments intended to measure certain parameters and means for recording the variations thereof in time. These instruments are set and, after a certain running time, a specialized tool: mandrel socket, is taken down to them at the end of a cable and they are taken up to the surface to read the data they have stored. This process is adapted for carrying out localized measurements in a location of the well, but the data recovered may only be accessed in a deferred way, by taking the instrument up to the surface.